Why Boeing can not use assumed on contaminated Runway?
Full power is required to counter the assumptions in contaminated performance. The published performance is not tested in those conditions; thus the performance values are approximate and that the exact type and depth of contaminant may not be known.
The effect of slush / spray impingement during takeoff is a retarding force, thus greater takeoff distances will be required. However this might help in an RTO, but then again the conditions may be inexact, the braking action incorrectly assessed/reported, and more runway already used in the takeoff roll.
Airbus view (NB this advice may be out of date, but the theory is still valid): https://www.scribd.com/doc/167078290...inated-Runways
Slide 13 – Use maximum thrust on contaminated runways.
The effect of slush / spray impingement during takeoff is a retarding force, thus greater takeoff distances will be required. However this might help in an RTO, but then again the conditions may be inexact, the braking action incorrectly assessed/reported, and more runway already used in the takeoff roll.
Airbus view (NB this advice may be out of date, but the theory is still valid): https://www.scribd.com/doc/167078290...inated-Runways
Slide 13 – Use maximum thrust on contaminated runways.
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There is no need to increase thrust if all that fails is just the one engine.
The effect of slush / spray impingement during takeoff is a retarding force, thus greater takeoff distances will be required. However this might help in an RTO, but then again the conditions may be inexact, the braking action incorrectly assessed/reported, and more runway already used in the takeoff roll.
Regarding slide 13, it's been a while since I've flown an Airbus and it was the older variety (310/300). Also, we didn't derate anyway so it wasn't an issue. I am unaware whether AB uses derates to improve payloads on contaminated runways but the original question seemed to imply that they do. The slide you referred to would seem to imply that they don't. Personally, if I were "King of the World", I would only reduce thrust on takeoff using the assumed temperature method as that would always make full thrust available if needed. For most airlines, it probably wouldn't matter much but if a lot of their operation were from contaminated runways, I could see the commercial value of using derated thrust.
Last edited by Gillegan; 21st Mar 2016 at 18:56.
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I take back what I said before, I meant to say the V1 will be lower for say 4 mm of slush than 9 mm of slush. The overall RTOW will lower for 9 mm of slush of than 4 mm. That rings true with slush/spray drag that causes a slower take off acceleration but helps in the Acc-Stop scenario.